The proper use of topical and oral corticosteroids
Jun 01, 2006
Corticosteroids are among the most used and misused medications in veterinary medicine. They exert a powerful, reliable, and rapid effect, and there is no viable, more effective therapeutic alternative in animals with certain skin conditions. Topical and oral corticosteroid therapies are considered the first choice for treatment of acute and chronic inflammatory skin diseases, particularly allergic dermatitis. In addition, they aid in the inflammation associated with some types of infections, primarily Malassezia dermatitis and otitis.
Using oral corticosteroids
The mineralocorticoid effects of corticosteroids are responsible for increased water consumption, subsequent increased urine output, and potential urinary incontinence. Prednisone and prednisolone exert a slightly stronger mineralocorticoid effect than methylprednisolone. Therefore, methylprednisolone may be used instead of prednisone or prednisolone in cases of undesirable increases in water consumption and urine output.
The most commonly administered oral corticosteroids are prednisone and prednisolone, the latter being more effective in cats. In dogs, a short regimen of prednisone or prednisolone usually results in mild to no side effects.
Most clinicians in private practice are regularly faced with challenging dermatologic cases, and a common question arises: How much prednisone is too much? No one can definitively answer this question, as different dogs respond in different ways. Some patients are unaffected by long-term prednisone administration, while others immediately demonstrate polyphagia, polydipsia and polyuria, or incontinence. Still others show signs of iatrogenic Cushing's disease—muscle wasting, a pot-bellied appearance, and muscle weakness—early on in therapy. The best approach is to try the safest treatment first, monitor the patient's response carefully, and adjust the therapeutic protocol if side effects become problematic or the condition does not respond.
Many dogs receiving corticosteroids will experience alterations in blood work, including variable increases in alkaline phosphatase activity; stress leukograms characterized by neutrophilia, lymphopenia, and eosinopenia; hyperglycemia; hypercholesterolemia; and occasionally a blunted cortisol response to adrenocorticotropic hormone (ACTH) administration.2 These changes are generally acceptable as they are rarely of clinical importance.
Other side effects commonly seen with long-term therapy include weight gain, a pot-bellied appearance associated with fat redistribution, alopecia (some hairs fracture, but most are arrested in the telogen phase), thin and poorly elastic skin, comedones, pustules, and secondary bacterial infections primarily involving the skin and the urinary tract. In one study, more than one-third of dogs experienced a urinary tract infection when treated with corticosteroids for longer than six months.3